The present invention relates to a shock absorber configured to generate a damping force by controlling a flow of hydraulic fluid in a cylinder during a stroke of a piston rod.
For example, Japanese Patent Public Disclosure No. Hei 11-159563 discloses a cylindrical shock absorber mounted on a suspension apparatus of a vehicle such as an automobile. This shock absorber includes a cylinder, and a cylindrical member disposed around the cylinder to thereby define an annular passage between the cylinder and the cylindrical member. Further, the cylindrical member includes a cylindrical protrusion radially outwardly formed on the sidewall of the cylindrical member, so that a branch tube in communication with the annular passage is integrally formed on the sidewall of the cylindrical member.
As disclosed in Japanese Patent Public Disclosure No. Hei 11-159563, in the shock absorber provided with the branch tube integrally formed on the sidewall of the cylindrical member to use it as a passage of hydraulic fluid, the cylindrical member and the branch tube should be sufficiently pressure-resistant to bear highly pressurized hydraulic fluid, and at the same time, should have a reduced wall thickness to achieve a lightweight structure.